Special moves (castling, en passant) in LLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is castling in chess and when can it be performed?

Castling is a special move involving the king and one rook. It can be performed if neither piece has moved before, there are no pieces between them, the king is not in check, and the squares the king passes over are not under attack.

beginner

Explain the en passant move in chess.

En passant is a special pawn capture that can occur immediately after an opponent's pawn moves two squares forward from its starting position, and your pawn could have captured it if it had moved only one square. You capture the pawn as if it moved only one square.

intermediate

What conditions must be checked in a system to validate castling?

The system must check that the king and rook have not moved, no pieces are between them, the king is not currently in check, and the king does not pass through or end on a square under attack.

intermediate

How does a system detect if an en passant capture is possible?

The system tracks the last move to see if a pawn moved two squares forward. If an opposing pawn is adjacent to the destination square, it can capture en passant on the next move only.

advanced

Why is it important to handle special moves like castling and en passant carefully in a chess system design?

Because these moves have unique rules and exceptions, handling them correctly ensures the game logic is accurate and fair, preventing illegal moves and maintaining game integrity.

Which piece moves during castling?

A Only the king

B King and queen

C Two rooks

D King and rook

Castling involves moving both the king and one rook simultaneously.

En passant can only be performed when:

A A pawn moves two squares forward from its starting position

B A pawn reaches the last rank

C A rook moves for the first time

D The king is in check

En passant capture is only possible immediately after a pawn moves two squares forward.

Which condition invalidates castling?

A King has moved before

B Rook has not moved

C No pieces between king and rook

D King is not in check

Castling is not allowed if the king has moved previously.

How long after the opponent's pawn moves two squares can en passant be performed?

A After two moves

B Any time later in the game

C Only immediately on the next move

D Only if the pawn reaches the last rank

En passant must be done immediately after the opponent's pawn moves two squares.

In system design, why track the last move for en passant?

A To check for checkmate

B To know if en passant capture is possible

C To update the score

D To reset the game

Tracking the last move helps determine if en passant is allowed.

Describe the rules and conditions that a system must check to allow castling.

Think about the king's safety and piece positions.

Explain how a chess system should detect and handle the en passant move.

Focus on the timing and position of pawns.